سید رضا عطارزاده حسینی^{*}^{1}، کیوان حجازی^{1}

**Purpose:** Allometry is a method to express the relationship between physiological and anatomical variables. It can be used to measure the vital capacity through mathematical equations. This study aimed at evaluating lung function indices to estimate the maximal aerobic power by respiratory gas analysis device and the allometric equation.

**Methods:** This study was a descriptive and correlational research. A total of 80 subjects were chosen by convenience sampling method. Then, their anthropometric characteristics and dimensions of chest circumference (diameter and depth of the chest) were measured, and Bruce test was used to measure maximal aerobic power. The Pearson correlation coefficient and multivariate regression analysis were performed using SPSS 16.

**Results:** There is a positive and significant relationship between vital capacity and maximal aerobic power (r=0.229, P=0.041) and also between the device vital capacity and formula vital capacity (r=1.00, P=0.00). Accordingly, the following model was developed (chest circumference×0.284)+(age×0.319)+(vital capacity×1.761)+inclination=Maximal oxygen consumption.

**Conclusion:** According to the study results, there is a significant correlation between device vital capacity and formula vital capacity. Thus, in order to predict the maximal oxygen consumption, in the absence of any other experimental methods, allometric equation can be used.